Photoinduced charge-separation and charge-recombination processes of fullerene dyads covalently connected with phenothiazine and its trimer (PTZn-C60, n = 1 and 3) with a short amide linkage were investigated. A time-resolved fluorescence study provided evidence of charge separation via the excited singlet state of a C60 moiety ( 1C60*), which displayed high efficiencies in various solvents; Φscs (quantum yield of charge separation via 1C60*) = 0.59 (toluene) to 0.87 (DMF) for PTZ1-C60 and 0.78 (toluene) to 0.91 (DMF) for PTZ 3-C60. The transient absorption measurement with a 6 ns time resolution in me visible and near-IR regions showed evidence of the generation of radical ion pairs in relatively polar solvents for both dyads. In nonpolar toluene, only PTZ1-3C60* was observed for PTZ1-C60, whereas PTZ3- 3C60* as well as the radical ion pair state in equilibrium were observed for PTZ3-C60. The radical ion pairs had relatively long lifetimes: 60 (DMF) to 910 ns (o-dichlorobenzene) for (PTZ)1.+-C60.- and 230 (PhCN) to 380 ns (o-dichlorobenzene) for (PTZ)3.+-C60 .-. The small reorganization energy (IVI) and the electronic coupling element (IVI) were estimated by the temperature dependence of the charge-recombination rates, i.e., λ -0.53 eV and IVI = 1.6 cm -1 for (PTZ)3.+-C60.-.
ASJC Scopus subject areas
- Physical and Theoretical Chemistry